GB2489619A

GB2489619A - Manipulative puzzle cube with spherical core

Info

Publication number: GB2489619A
Application number: GB1210318.0A
Authority: GB
Inventors: Steven Perrin
Original assignee: Seven Towns Ltd
Current assignee: Seven Towns Ltd
Priority date: 2012-06-12
Filing date: 2012-06-12
Publication date: 2012-10-03
Anticipated expiration: 2032-06-12
Also published as: GB2489619B; WO2012160395A2; GB201210318D0; WO2012160395A3

Abstract

A manipulative puzzle comprises a two-part hollow core 20, 22, face centre cubes (FCCs) 12a-f rotatably attached to the core, and edge cubes 14a-l and corner cubes 16a-h held in place by the FCCs. Each part of the core has bushings which support respective axles carried by three of the FCCs. Springs 106 located within the core and carried by the axles urge the FCCs inwardly for tensioning the puzzle. Clips fasten the parts of the core together. Each half-core may be generally hemispherical, may have three bushings 60, 62, 65, one of which 65 is in a polar location and two of which 60, 62 are in equatorial locations, and may have two equatorially located recesses 40, 42 for receiving bushings of the other half-core. Fastening of the parts of the core may be by clips 30, 32 extending from the equatorial bushings of one part which snap fit within sockets (26, 28, fig. 5) of the other part. The springs carried by the axles may be coil springs or leaf springs in compression, and the springs may be located in the core by washers 102 which frictionally engage with the ends of the axles (see figures 7a-7c).

Description

SPATIAL LOGIC PUZZLE

FIELD OF THE INVENTION

The present invention relates to a spatial logic puzzle which is useful as a plaything and/or to tcach spatial awarencss and a systematic approach to problem solving, and in particular to an improved mechanism for operation of such a puzzle

BACKGROUND TO THE INVENTION

Professor Emo Rubik is the inventor of the well-known Rubik's cube puzzle described in HU-B-170062 (1976), see also US-A-43781 16. It is based on the idea of providing a body made up from one or more sets of equivalent but identifiable pieces which are interconnected so that groups of pieces are relatively rotatable about three orthogonal axes. The pieces can exchange positions while the external shape of the body remains unchanged. Solutions of the puzzle are disclosed in a book by Tom Werneck, "Der Zauber-Wurfel", Wilhelm Heyne Verlag, 1981 (ISBN 3453-41449-7), the disclosure of which is incorporated herein by reference.

The general arrangement of a 3 x 3 x 3 Rubik's cube puzzle 10 is shown in Figs. 1 and 18. It will be seen that there are six face centre cubes 12a-12f, twelve edge cubes 14a-141 and eight corner cubes 16a-16h. Logically there are 27 cube positions. Cubes at 26 of them are visible from the exterior of the puzzle and the central cube position is concealed. The face centre cubes have a single visible face, the edge cubes have two visible faces and the corner cubes have three visible faces.

The principle by which the cube is constructed is that each face centre cube traps beneath it hidden formations of the remaining eight edge and corner cubes making up that face so that the face centre cubes collectively hold the remaining cubes in position, and an internal mechanism permits the nine cubes of a layer forming any one of the six puzzle faces to be rotated relative the cubes of the other two layers so that the pieces can be displaced from and returned to the solved state by successive rotations of the various faces. The blind faces of the cubes together define division planes permitting relative rotation to take place, although the division planes may be apparent only from the exterior of the puzzle and may not be continuous from one side of the puzzle to the other.

An exploded view of a 3 x 3 x 3 Rubik's cube puzzle of known construction appears in Fig 18 which reveals the internal structure. A spider 320 occupies the central cube position with its six arms formed with bores which receive rivets 322 that attach cach of the face ccntrc cubes 3 12a-3 12f to a rcspcctive arm for rotation thereon, the rivets extending through bores in the face centre cubes. Springs 324 in compression between heads of the rivets and the face centre cubes urge the face centre cubes inwardly and set the tightness of the puzzle. Each rivet is concealed by a cube cover 326.

The edge cubes 3 14a-3 141 have two visible faces, a blind internal face for abutment with a face centre cube, two lateral faces for abutment with adjacent edge cubes and a diagonally inward extension 328 whose width is about one third of the width of the cube. That extension 328 is generally of quadrant outline and its sidewalls lie in planes parallel to and spaced inwardly from the adjacent edge cube blind lateral faces. It fits between arms of the spider 320 for stabilising the attitude of the edge cube and rotatably positioning the edge cube relative to the spider.

The corner cubes 3 16a-3 16h have diagonal extensions 330 that fit under the edge cubes and each abut the inward extensions 328 of an adjacent trio of edge cubes.

For example the extension on corner cube 31 6d aligns with and fits between the extensions on edge cubes 314a, 3141 and 3 l4d. Each extension 328 is generally block-shaped with a chamfered and radiused outer corner.

A substantially complete end face of the puzzle appears in Fig 18, with the centre face cube 3 12b shown exploded. In the resulting window there appear four extensions 328 for the four edge cubes 314c, 314e, 314h and 314f and four extensions 330 for each of the corner cubes 316b, 316c, 316f and 316g (only a few of these are seen in Fig. 18, but all of them would be seen looking along the axis of the rivet for cube 3 12b). In the assembled puzzle all eight of these extensions are trapped beneath the face central cube 3 12b, so that the edge and corner cubes are held in place when the puzzle is at rest and while a user is attempting to solve it by rotation of the nine cubes of that face relative to the cubes of the other two puzzle layers. The puzzle is symmetrical and the same arrangement is present on the other five faces. The corner piece extensions 330 are each trapped behind three face centre cubes so that the corner pieces are firmly held whereas the edge cube extensions 328 are each trapped behind only by a single face central cube. Disassembly of a cube can be initiated by rotating one of the layers to an angle of 45° relative to the other two layers and then prising an edge cube of one layer away from the other two layers e.g. using a screwdriver.

However the lesser degree of entrapment of the edge cubes means that if a puzzle should fail e.g. during speed-cubing it is likely to be at one of the edge cubes which may pop out from the remainder of the puzzle. Another problem is that care has to be taken to insert the rivets 322 to the required depth in the spider 320 to achieve a desired and uniform cube tension and close assembly tolerances are required. A further problem associated with the above mechanism is that it is relatively unforgiving of misalignment which again is a difficulty in speed-cubing where the ability to rotate faces of the puzzle when in a slightly misaligned state (called by users "comer-cutting" or "reverse corner cutting") is valued. When new a cube of conventional structure cannot be rotated when its faces are misaligned, but on wear, lubrication and possibly user modification e.g. by user disassembly and sanding away blind faces a degree of corner-cutting or reverse corner-cutting may be possible without lockup.

A variant of the intemal structure shown in Fig. 18 is described in Verdes WO 2004/103497 which describes a range of cubes from 2 x 2 x 2 to 11 x 11 x 11 including a 3 x 3 x 3 cube. The basic structure continues to be based on a spider occupying the central cube position with its six arms formed with bores which receive rivets or screws that attach each of the face centre cubes to a respective arm for rotation thereon, the rivets extending through holes in the face centre cube and carrying springs that fit between a head of each rivet or screw and the head of the cube to urge the cube inwardly and tension the puzzle. In the 3 x 3 x 3 embodiment he face centre cubes comprise a visible face and four sidewalls terrninating in an outwardly facing part spherical surround. Edge cubes are formed with lateral projections for entrapment within formations of the adjacent corner cubes and have a central quadrant-shaped inward extension closely resembling the inward extension 328 in the structure shown in Fig 18. Each corner cube has at its diagonally inward-facing corner a part spherical surface carrying a diagonally-directed spacer post terminating at an octant-shaped internal extension, the gap between the part-spherical surface and the octant-shaped extension providing a space for the surrounds of the face centre cubes and the lateral projections of the edge cubes to pass. A problem addressed by Verdes is slow rotation experienced by competftion users, especially for the higher cubes, and the solution is based on right conical surfaces for the individual cubes in place of cylindrical surfaces, such surfaces being apparent for the 3 x 3 x 3 variant for a face centre cube in Fig, 3.3 and for an edge cube in Figs. 2.3.2, 3.2.1 and 3.2.2. It is not apparent that a puzzle of this kind has ever been successfully produced or marketed.

WO 83/01203 (Torres) discloses a 3 x 3 x 3 cube puzzle in which there is no internal spider connector as in a conventional Rubik's cube. Instead individual elements are profiled to lie on part of an imaginary spherical surface. Each element defines with each adjacent element an element pair having a tongue-and-groove inter-engagement structure substantially along the spherical surface. However, the edge and corner cubes are not mechanically hooked behind face centre cubes as in a conventional Rubik's cube. Puzzles of this kind have not proved successful.

The Feliks Pillow Cube is not described in any published document that the applicants have been able to identify, but is shown at (Mefferts, http://www1youtube.cocn/watch.?v:=7U6_i 6eX1c\).

It has a spherical core formed in two parts fixed together with screws. There are two face centre cubes in "polar" positions and four face centre cubes in equatorial" positions. The face centre cubes are attached to the core by fixing screws having plain shafts and threaded inner ends, the fixing screws passing into the core and being received in respective cup-shaped socket members within the core that are engaged by the threaded ends of the screws. The inner ends of the fixing screws carry coil springs which are in compression between the sockets and adjacent shell regions of the core to urge the face centre cubes inwardly and tension the puzzle. Edge cubes have arcuate retaining members that hook under the face centre cubes and corner cubes have triangular retaining plates. A similar cube puzzle which is tournament-legal because it does not have the pillowed faces is sold by China Magic Cube under the name MF8 Legend 3 x 3 x 3 Magic Cube and has the same core and internal piece structure as the Feliks Pillow cube. However, reviews show that performance is affected by the tightness or otherwise of the screws and as there are six screws even tensioning of all the faces may not be achieved. The core is mechanically complex and time-consuming to assemble and retention of the edge and corner cubes could be improved, especially in the vulnerable position where one face has been twisted to about 45° relative to the other two faces of the cube, the cube being vulnerable to "popping". Cubes that are satisfactory for specialist aduh users may not be satisfactory for the mass market and in particular for sale to users under 14 years of age. In order to be considered safe for sale to under 14 users puzzles have to satisfy a range of safety standards of which the most relevant are a drop test in which the puzzle is dropped ten times onto a hard surface from a height of 1.4, (4.Sft) and a pull test conducted to a pulling strength of 90N (10kg) and the puzzle should be capable of surviving such tests without any of its component cubes popping. A cube of this design is not optimised for high-volume production because of its complexity and component inventory.

It is an object of this invention to provide core and piece structures which may alleviate some or all of the above mentioned problems.

SUMMARY OF THE INVENTION

An embodiment of the invention provides a two-part spherical core for a manipulative puzzle, wherein formations on each part provide for core assembly by clipping the parts together and/or each part has bushings for rotatably supporting axles of face centre cubes. In embodiments clip formations arise from two equatorially located bushings of one core part for reception in in catch sockets of the other core part.

The equatorial bushings are conveniently spaced 180° angularly apart.

Embodiments of the present puzzle have the springs that tension the puzzle positioned within the core so that they may form part of the core e.g. being in the form of leaf springs tensioning at least some of the face centre cubes or being in the form of coil springs located within the core for tensioning at least some of the face centre cubes.

In one aspect the invention provides a manipulative puzzle comprising a two-part hollow core, face centre cubes pivotally attached to the core and edge and corner cubes held in the puzzle by the face centre cubes, wherein: axles are carried by the face centre cubes; each part of the core has bushings that support axles of three of the face centre cubes; springs within the core and carried by the axles urge the face centre cubes inwardly for tensioning the puzzle; and clips fasten the parts of the core together.

As is apparent, the puzzle may be of the 3 x 3 x 3 cubic type, and the individual pieces when viewed from the exterior of the puzzle may have the shape of regular cubes. Although other shapes are possible e.g. as in a pillow cube, these are less preferred.

In further embodiments there is provided a manipulative puzzle comprising a two-part hollow core, face centre cubes pivotally attached to the core and edge and corner cubes held in the puzzle by the face centre cubes, wherein axles are carried by the face centre cubes, springs within the core and carried by the axles urge the face centre cubes inwardly for tensioning the puzzle and each part of the core has bushings that support axles of three of the face centre cubes. The bushings may be of plastics material. The face centre cubes may be of a first plastics material and the axles may be discrete components that pass through apertures OR BORES in head regions of said cubes and are of a second low-friction plastics material. For example, the axle may be of aeetal and the head region may be of ABS.

Further embodiments provide a manipulative puzzle comprising a two-part hollow core, face centre cubes pivotally attached to the core and edge and corner cubes held in the puzzle by the face centre cubes, wherein axles are carried by the face centre cubes, springs within the core and carried by the axles urge the face centre cubes inwardly for tensioning the puzzle and clips fasten the parts of the core together.

In a further embodiment the invention provides a manipulative puzzle comprising a core, face centre cubes pivotally attached to the core and edge and corner cubes entrapped and retained by the face centre cubes, wherein: the face centre cubes comprise a surface region providing a visible face, four blind faces and a retainer located at the inner ends of the blind faces, said retainer surrounding and projecting outwardly from said faces; the edge cubes each have side faces each formed with a lateral retainer projection for entrapment beneath a portion of an adjacent corner cube and an extension spaced inwardly from its visible faces for entrapment beneath adjacent face centre cubes, said extension being spaced from the remainder of the edge cube to permit the retainer of the a face centre cube to pass as a face of the puzzle is relatively rotated; and the corner cubes have a concave surface at a diagonally inner corner for slideable reception of the retainer of a face centre cube and of the lateral retainer projection of an edge cube, a retention plate positioned so that regions thereof are trapped beneath the face centre cube, and a spacer maintaining the retention plate at a spacing inwardly of the concave surface to permit passage of the retainer of a face centre cube and of the lateral retainer projection of an edge cube.

In a further embodiment there is provided a manipulative puzzle comprising a corc, face centre cubes pivotally attached to the core and edge and corner cubes entrapped and retained by the face centre cubes, wherein internal faces of the edge cubes are bevelled for realignment of a misaligned face of the puzzle on relative rotation of another puzzle face.

In a yet further embodiment of the aforesaid puzzle the edge cubes each have side faces each formed with a lateral retainer projection for entrapment beneath a portion of an adjacent corner cube, opposed ends of the lateral retainer projections being bevelled for restoring alignment of a slightly misaligned puzzle as one group of cubes is rotated relative to the others. Tn embodiments the lateral retainer projections carry inwardly directed spacers and the bevels are formed at opposed ends of the spacers.

In embodiments there is a relationship between the improved retention provided for the edge and corner cubes and the tensioning force needed to be exerted at the face centre cubes. In particular relatively low tension may be provided by the springs because the edge and centre cubes in embodiments are more secure against popping, the puzzle can be more flexible and smooth and fast to turn, and the reduced spring resistance can also assist corner cutting and reduce jamming consequent upon non-alignment.

In a further embodiment the invention provides a corner cube for a 3 x 3 x 3 cubic manipulative puzzle including: a concave surface at a diagonally inner corner for slideable reception of the retainer of a face centre cube and of the lateral retainer projection of an edge cube; a retention plate positioned so that regions thereof are trapped beneath the face centre cube; outwardly directed tabs at edges of the retention plate defining return hooks for entrapment beneath face centre cubes for providing resistance to accidental removal of the corner cube from an assembled puzzle

S

Embodiments of the above corner cube may comprise a spacer for maintaining the retention plate at a spacing inwardly of the concave surface to permit passage of the retainer of a face centre cube and of a lateral retainer projection of an edge cube.

Features of the above embodiments may be used interchangeably in combination with one another. The term "manipulative" in relation to the puzzle means that solution is by user manipulation of the pieces of the puzzle.

BRIEF DESCRIPTION OF THE DRAWINGS

How the invention may be put into effect will now be described, by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is an exploded view of a puzzle according to the invention; Fig. 2 is a perspective view of a core and six face centre cubes forming part of the puzzle of Fig. 1; Fig. 3 is an oblique perspective view of a half-core forming part of the core of Fig. 2 and showing the interior of the half-core, Fig 4 is another view of the interior of the half-core closer to an axis thereof and Fig. 5 is an exterior view of the half-core; Fig. 6 is an interior of the half-core carrying three face centre cubes; Fig. 7a is a perspective view of a face centre cube showing also an associated coil spring and retaining washer, Fig. 7b is a perspective view of a second embodiment of a face centre cube with its head and a pivot shaft thereof formed as discrete components, Fig. 7c is a perspective view of a third embodiment of a face centre cube also showing a coil spring and retaining washer, and Figs 7d and 7e are exterior oblique and interior oblique views of a fourth embodiment of a face centre cube and associated components for use in speed-cubing; Fig 8 is an exploded view a core, six face centre cubes and an internal axle anti-rotation component for use in speed-cubing; Figs 9a-9c are views of the axle anti-rotation component of Fig. 8; Fig 10 is a view of a combined spring and retaining washer; Fig 11 us a view of a corner cube with its components exploded; Fig I 2a is an oblique exterior perspective view of an edge cube also showing a retention plate of an adjacent corner cube and Figs 12b and 12c are oblique interior perspective views of the edge cube; Fig. 13 is an oblique view of four face centre cubes and four edge cubes together defining a middle layer of the puzzle; Fig 14 is an oblique interior view of a face centre cube, four edge cubes and four corner cubes together defining an outer layer of the puzzle; Fig 15 is an oblique view showing four corner cubes of an outer layer of the puzzle and a face centre cube and an adjacent edge cube of the middle layer of the puzzle, the middle and outer layers being relatively rotated by 45°; Fig 16 is an oblique internal view showing adjacent face centre, edge and corner cubes of the puzzle; Fig. 17 is a view of the puzzle with one face at a slight angle to the others as in "corner-cutting" and with one corner cube of the angled face removed; Fig. 18 is an exploded view of a conventional Rubik's cube.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In the following discussion, references to "upper", "lower", "polar" and "equatorial" are adopted for convenience and refer to the puzzle in the attitudes in the drawings. They map e.g. to first and second directions in an arbitrary cube attitude.

An exploded view of an embodiment of the present puzzle appears in Fig. 1. It incorporates a two-part hollow spherical core formed of hemispherical members 20, 22 that clip together. The hemispherical core member 20 provides rotational support for three face centre cubes, one of them 12a being in a "polar" position and the remaining two 12b and 12d being in "equatorial" positions. Similarly the hemispherical core member 22 rotationally supports face centre cube l2f in a "polar" position and the remaining two face centre cubes 12c and 12e in "equatorial" positions. Each face centre cube has an axle extending through a bearing in its respective core member 20 or 22 so as to be supported in a fixed attitude relative thereto, carries a compression coil spring 106 and is fastened to the core member by spring barb washer 102. Three of the face centre cubes 12a, Jib, 12d may be assembled to core member 20 as in fig. 6, similarly the other three face centre cubes 12c, 12e and 12f may be assembled to core member 22, after which the core members 20, 22 may be clipped together to give a core assembly as shown in Fig. 2.

The puzzle further incorporates twelve edge cubes 14a-14k and eight corner cubes 1 6a-1 6h which can be hooked successively into the core sub-assembly to complete the puzzle, the edge and corner cubes being held in place by the face centre cubes 12a-12f.

The various components of the puzzle may be injection mouldings in a plastics material such as ABS, except for the coil springs 106 which are of metal and the barb washers 102 and face centre cube axles (when formed as separate components) which are injection mouldings in aeetal (polyoxymethylene) which is preferred, nylon or similar strong but slightly resilient (and in the ease of axles low-friction) plastics material.

Each half-core may be generally hemispherical, may have three bushings, one of which is in a polar location and two of which are in equatorial locations, and may have two equatorially located recesses for receiving bushings of the other half-core.

Fastening of the parts of the core may be by clips arising from the equatorial bushings of one part that are snap fits within sockets of the other part.

The axles may carry coil springs or leaf springs in compression.

Figs 3-5 show a half-core 20 in more detail. It incorporates a bushing 65 in a central or polar location to serve as a bearing for the axle of cube 12a and an equatorially located diametrically opposed pair of bushings 60, 62 to serve as bearings for axles of cubes 12b, 12d. The bushings have regions extending into the interior of the half-core and regions 64, 66 projecting radially outwardly of the half-core as shown.

Regions of the half-core adjacent the bushings as viewed from its exterior are formed with recesses 34, 35 (Fig. 5). Reinforcing walls 85, 87 to either side of the bushing 62 and directed parallel to its axis extend inwardly of the half-core; part of these walls coincide with recess 34. Similar walls 77, 79 to either side of the bushing 60 and directed parallel to its axis extend inwardly of the half-core and again coincide with recess 35.

A pair of equatorially located diametrically opposed recesses 40, 42 of semi-circular shape is defined in the core 20 at positions spaced 90° apart from the bushings 60, 62 for receiving equatorially located bushings of the other core half 22 when the core halves are clipped together. Each recess 40, 42 corresponds to a thickened region of the shell of the half-core, the thickened region being outwardly projecting as shown, the thickening being provided for spreading load while the puzzle is being used.

Reinforcing walls 73, 75 extend inwardly of the core to either side of the recess 40 and are directed parallel to the axis of the recess 40; similar walls 81, 83 extend inwardly of the core to either side of the recess 42 and are again directed parallel to the axis thereof.

The bushing 65 is surrounded by a circular reinforcing wall 71 which is joined to shallow extensions of the walls 73,75, 77,79, 8 1,83 and 85, 87 as shown. Further reinforcing walls 70,72, 74,76, 7 8,80 and 82,84 extend from positions behind inner ends of walls 73,75, 77,79, 81,83 and 85, 87 to the shell of the half-core. These reinforcing walls together define an interrupted rectangular pattern of reinforcing webs for the shell and bushings, although other reinforcement patterns could be possible depending on design preferences and convenience in the moulding process.

Clips 30, 32 within the shell arise from the bushings 60, 62 and are formed at their ends with outwardly facing heads 56, 58. The clips are configured for insertion into shell apertures 26, 28 located between the walls 75, 77 and 81, 83 adjacent the recesses 40, 42, the apertures 26, 28 being located 90° apart from the recesses 34, 35 as can be seen in Fig. 5. Locking members 36, 38 in recesses 26, 28 fit behind the clip heads 56,58 as shown in Fig. 2 to resist unlocking of the clips once the half-shells 30, 32 have been clipped together. The arrangement in which the clips 30, 32 arise from the bushings 60, 62 is convenient from the moulding standpoint, and the clip and socket arrangement is both robust and forgiving. Each pair of clips 30, 32 of each half-core in the assembled core holds the core halves together in a plane passing through the centre of the core, and because there are two such pairs of clips, one on each core half, the core halves are strapped or clipped together in two planes at right-angles to one another.

Various face centre cube embodiments are shown in Fig 2 and Figs 7a-7e. Each cube has a head region 50 comprising a visible face and four sidewalls corresponding to division planes of the puzzle. The sidewalls terminate at an outwardly-facing part-spherical surround 52 having four edges 54 corresponding to each sidewall. Each of the edges 54 is of arcuate profile, and has a radiused outer region leading to a relatively short generally planar region directed parallel to the respective sidewall which in trun leads to a radiused inner region. The purpose of the surround is to provide improved retention of edge and corner cubes as described below. The face centre cubes may incorporate shafts or axles wholly or partly of plastics which may be formed integrally with the head region or may be formed as separate components.

Fig. 6 is a view from the interior of one of the half-cores showing three face centre cubes 12a, 12e, 12e supported in the bushings 60, 62, 65. Heads of the cubes appear together with respective springs 104, 105, 106 and retaining washers 98, 100 and 102. In the bare half-core sub-assembly of Fig. 6 the cube heads are unsupported and ahhough in the fully assembled cube they are positioned by adjacent edge and corner cubes they are not positively located. In this embodiment the puzzle is self-tensioning by virtue of the coil springs 104. These springs are in compression between the inner ends of the bushings 60, 62, 65 and the washers 98, 100, 102 with the resuh that the face centre cubes are urged towards the outer ends of the bushings with a load determined by the degree to which springs become compressed. In Fig 6 and in the bare core sub-assembly of Fig. 2 the cube bosses may be in contact with the outer ends of the bearing bushes, but as face and edge cubes are added to fully assemble the puzzle the face centre cubes are moved slightly outwardly without bringing the washers 98, 100, 102 into contact with formations on the inner face of the core half-shells 20, 22. There is therefore float along the axles 110 (Fig. 7a) controlled by the coil springs 104, 105, 106 or in the Fig. 10 embodiment below by leaf springs 162, 164. The compression in the springs 104 is determined by the geometry of the moulded components and the tension in the puzzle is determined by the compression and by the mechanical properties of the springs, neither of which depend significantly on assembly tolerances.

Lack of contact between the washers 98, 100, 102 and formations within the half cores 20, 22 whilst important for "float" means that the washers play no part in positioning the face centre cubes. The positioning and support duty is performed wholly by the bushings 60, 62, 65 which are cylindrical and can be moulded with their interiors of circular profile (within moulding tolerances) and of sufficient axial length both to provide location and support for the axles that pass through them and to withstand loads, and in particular lateral forces incidental to user rotation of the cube faces. In theory it would be possible to provide half-bushings at the equatorial locations which would together define complete bushings when the core halves were fastened together, but this option is less preferred because lateral forces on the cube axles would be reacted by the clips or other fastening means and it would be difficult to prevent such forces at least to some extent separating the half-bushings with consequent loss of location and support. In particular when the axles are wholly or partly of acetal or other plastics it is desirable to have complete cylindrical bushings as part of the spherical core structure. Centre cube rotation as cube faces are rotated during use of the puzzle can have two mechanisms. Firstly the axles can rotate within the bushings. Secondly where the axle is a discrete component as in Fig 7b rotation can be between the head of the cube and the flanged outer end of the axle. It is uncertain which mechanism will predominate, and in embodiments both mechanisms may play a part.

Fig. 7a shows an embodiment of a face centre cube the kind shown in Figs 1 and 6. It is a one-piece moulding with on its inner face a boss 44 from which arises an axle terminating at a head 92. Spring 104 fits onto axle 110 and washer 100 can be pushed over head 92 until its spring barbs locate into catch recess 112.

Fig. 7b shows a second embodiment in which cube 12a' has a boss 44' formed with a through hole via which axle 117 having retaining flange 115 can be inserted.

Forming the cube as a single moulding or as separate components is a matter of convenience depending primarily on moulding considerations. However, the head of the cube may be made in ABS or other plastics material, whereas the axle may be made of a second plastics material having low friction properties e.g. acetal. As in Fig. 7c, the head of the cube is formed with a recess into which a separate cover is engageable by clips that snap into catches formed in the recess..

In Fig. 7c there is shown a cube 12" having boss 44" on its inner face, axle 110" arising from the boss and a bifurcated end region extending through head 92" and catch recess 112". A coil spring 104" fits to the axle as before and resilience to permit plain washer 100" to be engaged onto the axle is provided by the end bifurcation.

In the above embodiments the puzzle is self-tensioning by virtue of the coil springs 104 as explained above.

Some speed-cubers prefer to adjust the tension themselves and an embodiment of a face centre cube configured to have increased adjustability is shown in Figs 7d and 7e. Cube 12" has a head 50" and a separate cover 120 engageable into head recess 122 by clips 124 that snap into catches 126. A fastening screw 132 can be passed into and through flanged collar 128 that fits into recess 130 formed in the head. Boss 44" is stepped corresponding to the flange and the lesser-diameter barrel of the retaining collar 128. Coil spring 136 fits onto axle 134 and is retained by square pyramidal head 135.

Screw 132 projects through collar 128 and boss 44" and is threadedly engaged into a fixing hole or bore 133 at the outer end of axle 134. Rotation of the screw 132 increases or decreases the distance by which ft has entered the bore 133 and hence increments or decrements the tension provided by compression spring 136. It should be mentioned that this cap and snap-in cover arrangement can be used for other embodiments of the face centre cube, and also for edge and corner cubes if desired so that there may be provided snap-in coloured inserts for the various face, edge and corner cubes instead of more usual adhesive coloured identifiers.

In the speed-cubing embodiment of Figs 7d and 7e the axle 134 has to be held in a fixed angular position so that ft is not rotated when screw 132 is rotated. Instead the head of the cube 12" rotates on the collar 128. An exploded view of the cube core in this embodiment appears in Fig. 8, from which ft is apparent that an anti-rotation device fits wfthin the core, that device being shown in greater detail in Figs 9a-9c. It is moulded wfth main plates 142, 144 and generally U-shaped auxiliary plates 146, 150, 148, 158, 152. The device 110 has six pairs of at least two fixed faces e.g. 154, 156 and in some positions a third face defining sockets into which axle heads 135 fit without freedom to rotate. The plates are configured to fit into the core halves within the various internal reinforcing walls. During assembly the six face centre cubes are fitted to the core halves as previously, after which the anti-rotation device 140 is fitted to that half, Then the second core half is offered to the first core half and the two are clipped together as previously. The sockets each have at least one open side by which the head of the respective axle enters, and the play provided by the springs suffices for the device 140 to be inserted with the cubes in place on the core members 20,22.

In place of coil springs, resilience and self-tensioning may be provided by leaf springs 162, 164 e.g. attached to barb washer 160 as in Fig. 10.

A corner cube according to an embodiment of the invention is shown in Fig. 11 and in this embodiment is a three-component assembly. A three-sided cover 170 provides the three visible faces for the cube and has four inwardly-facing edges that are rebated (176, 180) to receive four outwardly-facing edges e.g. 173, 186 of body 172, the cover and body being attached by sonic welding or other convenient means. Three convergent inwardly-facing edges 188, 200, 202 of body 172 have relatively small radii adjacent the vertices of the cube which flare into larger radii away from the vertices in order to allow passage of centre cube surround 52 e.g. when corner-cutting and lead to a cut-off defined by a part spherical inwardly facing concave surface 211. From the centre of that surface there arises a triangular pyramidal spacer defined by three faces e.g. the face 206 with bevelled corners 208, 210, 212 to allow passage of portions of adjacent edge cubes in a misaligned or corner-cutting state. A post 204 also of generally triangular shape arises from the inner end of the spacer and is directed diagonally inwards. A generally triangular retaining plate 174 has a concave inner face shaped to confirm to the outer shell of the core above which it is moveable as faces of the puzzle are relatively rotated. It is sonically welded or otherwise attached at its centre to the post 204. The plate 174 is provided for retention of the corner cube to the assembled puzzle where it hooks behind a set of three adjacent face centre cubes e.g. 12a, 12b, 12c, the surround 52 increasing overlap with and serving to improve retention. The plate 174 is spaced apart from spherical surface 211 by the pyramidal spacer, the spacing being such that as the cube is rotated a surround 52 of one of the face centre cubes can pass between them. Edges 218 of the plate 174 carry, midway along their length, reverse-facing tabs 220 also for improving corner cube retention. WO 83/0 1203 (TolTes) also discloses superficially similar corner cubes for a cube puzzle, but the way in which the corner and face cubes are held in position is by a tongue-and-groove arrangement which is fundamentally different from the hooking retention of a conventional Rubik's cube or the arrangement described herein. The Tones corner cubes have triangular retaining plates, but the edges of these plates lie within the planes defined by the sides of the cube and do not extend beyond those planes as does the plate 174, the reason being that the Tones plates are not required to hook behind the face centre cubes. In the MF8 Legend and Feliks Pillow Cubes the corner cubes carry triangular retaining plates (but without reverse-facing tabs) but these are attached to the cube body without any spacing, such spacing being unnecessary because the face centre cubes are plain and have no surround extending beyond the division planes defined by sides of those cubes.

An edge cube according to an embodiment of the invention is shown in Figs 12a-12c. Tn this embodiment it is a one-piece moulding and has two visible faces and two blind lateral faces 230, 231 that terminate at generally arcuate edges 232.

Reinforcing webs 240, 241 provide support for a quadrant-shaped inward extension 238 that occupies about one third of the width of the cube with its sidewalls lying in planes parallel to and spaced inwardly from the adjacent blind lateral faces 230, 231. In the assembled cube the extension 238 is hooked behind a pair of edge cubes. Curved inner edges of the extension 238 correspond to the curvature of the core over which they have to travel. Outer faces of the extension 238 are linear and are spaced apart from adjoining portions of the edge cube to allow a surround 52 of a face centre cube to pass between them. Bevelled corners 239 of the extension 238 permit other pieces of the puzzle to pass in a misaligned or corner-cutting state. The blind lateral faces carry oppositely directed laterally extending projections 234 which have part spherical outer surfaces that fit slideably beneath the concave surfaces 211 of adjoining corner cubes and that terminate in inwardly directed spacers 236 directed generally parallel to the lateral faces on which they are carried. Central faces 242 of the spacers are configured to abut corner cube spacer faces 206 and are bounded by bevelled faces 244, 246 for assisting realignment of a slightly misaligned cube e.g. in corner-cutting or reverse corner-cutting. In Tones WO 83/0 1203 there is nothing corresponding to the extension 238 and although there are laterally extending projections there are no structures corresponding to the spacers 242. In the MF8 Legend and Feliks Pillow Cubes there is no gap between the inward extension and the body of a face centre cube and that cube has no lateral projections.

A middle layer of the puzzle is shown in Fig. 13 and is defined by face centre cubes 12a, 12b, 12f and 12d and by edge cubes 14a, 14c 14h and 14j. It will be noted that surrounds 54 and edges 56 of the face centre cubes and retaining projections 232 and spacers 234 of the edge cubes form a substantially continuous circle and in the view shown project above the division plane defined by the blind lateral faces of the face centre cubes and the edge cubes, that plane also defining a division line of the puzzle.

The middle layer is symmetric, so that its other face has the same appearance and the same projecting layer defined by surrounds and retaining projections and spacers. It will be noted that the retaining projections 234 of the edge cubes have main faces 242 and bevelled faces 244, 246 at their opposite ends to accommodate misalignment of the puzzle and urge the puzzle towards correct alignment as the cubes of one face are rotated during corner-cutting. With these bevels, misalignment of up to about 150 can be tolerated without rotation of the cubes being interfered with, which is a benefit during corner-cutting. The inner ends of the surrounds 52 of the edge cubes and the inner ends of spacers 234 of the face centre cubes lie on a circle of diameter just sufficient to clear the cube core. It will be appreciated that there are three sets of cubes that can make up such a middle layer, the other two cube sets forming layers of this kind including the cubes 14a, 12c, 12f and l2e and 12b, 12c, 12d and l2f Fig. 14 shows one of the six puzzle outer layers formed by a face centre cube, edge cubes 14b, l4e. 14h, 14k and corner cubes 16a, 16b, 16f and 16i. The axle of the face centre cube is apparent as are inward extensions 238, 238', 238" and 238" of the edge cubes and part spherical retaining plates 174, 174', 174" and 174" (each slightly less than an octant of a circle) of the corner cubes. It will be seen that two lateral edges of each retaining plate e.g. 174' abut adjacent inward extensions e.g. 238 and 238'. It may also be seen that a circular space exists to the outside of the extensions and plates, the space being bounded by concave surfaces 211 of the corner cubes and by the retaining plates, the adjoining portions of the edge cubes being open as shown. By comparison of Figs, 13 and 14 it can be seen that the inner ends of projection spacers 234 of the edge cubes and the inner ends of surrounds 54 of the face centre cubes can fit into and rotate within this space. It will also be appreciated from the symmetry of the cube that the other five faces, when viewed from the interior, are similar to Fig. 14.

Fig. 15 shows the effect of the barbed return hook 220 of the inner retaining plate 174 of the corner cube. The triangular retaining plate fixed to the post of the corner cube has three curved surfaces which each has a tab 220 creating a barbed return hook. This tab prevents the corner cube parts from being forcibly pulled out of the assembled cube. Fig 15 shows a state in which an outer layer of the puzzle containing edge cubes 16a, 16d, 16h and 16i has rotated to 45° relative to the central layer of which face centre cube 12e and edge cube 14h. It can be seen that the tab 220 is hooked behind the surround 52 of face centre cube 12e, thereby providing a resistance to accidental removal of that cube from the puzzle.

Fig. 16 is a view of face centre cube 12b, edge cube 14e and corner cube 16f with the retaining plate of that cube removed. Overlap of the surround 52 of the face centre cube 12b and the inner part-spherical surface 211 of an adjacent corner cube 16f is apparent, as is overlap between projection 234 of edge cube 14e and the surface 211.

In that view central face 242 of the spacer 236 butts against and is slideable past a triangular side face 206 (Fig. 11) of the pyramidal spacer forming part of edge cube 16 It is also apparent in this view how projection 238 of edge cube 14e is hooked or trapped behind surround 52 of face centre cube 12b.

Fig. 17 is a view of the puzzle with its face containing cube 12c at a slight angle to the other two faces containing cubes 12a and 14e and with the cube 16d not shown (although the post thereof remains). It can be seen that projection 234 and spacer 236 of cube 14a are in cam-like engagement via bevelled faces with projection 234' and spacer 236' of cube 14h. Clockwise or anticlockwise rotation of the cubes of the face containing cube 1 2a (corner-cutting or reverse corner-cutting) will by this cam action restore the cubes of face 1 2c into alignment, thus facilitation rotation.

Features of at least some embodiments of the invention are: (a) the arrangement of the core in which pivot posts of each centre cube are assembled by snap fit to the core. This can saves cost through a reduction in component inventory and speedier assembly, and is a more reliable design as the tolerance is controlled by the parts and not any assembly apparatus.

(b) The internal chamfered edges of the side hooks of the edge cubes that become active as cam surfaces to push each other out of the way as the parts move. The benefit of this is to increase speed and smoothness of turning to allow for some miss-alignment of the parts while permitting them to turn.

(c) Similar to (b) above the small chamfer of the inner surfaces of the corner cubes are active cam surfaces which act upon the flange of the centre cube to allow for some misalignment of the parts while permitting them to turn. In some embodiments of the invention specific chamfered edges may act as active cams to aid the cube parts to self-align. Specific chamfers are identified above and these act upon any edge or corner they pass as the parts rotate. The chamfer allows for a gap to open between the parts which if not chamfered would create a corner with no gap. Without the gap the parts cannot move from one axis of rotation to another without being first perfectly aligned.

This gap allows the parts to move with up to 100 of misalignment where they would otherwise jam. The actual chamfer edge then also become active as a cam surface forcing the parts to move and auto align self-correcting their position. This is a desirable feature for the smooth fast turning of the cube.

It will be appreciated that modifications may be made to the embodiments described above without departing from the invention. For example, the face centre cubes could be used without surrounds, the edge and corner cubes then resembling those used in the Pillow Cube or the MFS Legend cube, although advantages in terms of secure retention of the edge and corner cubes would then be lost.

Claims

CLAIMS1. A manipulative puzzle comprising a two-part hollow core, face centre cubes pivotally attached to the core and edge and corner cubes held in the puzzle by the face centre cubes, wherein: axles are carried by the face centre cubes; each part of the core has bushings that support axles of three of the face centre cubes; springs within the core and carried by the axles urge the face centre cubes inwardly for tensioning the puzzle; and clips fasten the parts of the core together.
2. The puzzle of claim 1, wherein each face centre cube and its axle is formed as a one-piece injection moulding.
3. The puzzle of claim 1, wherein each face centre cube is formed with a central aperture and an axle having a retaining flange at its outer end fits through the aperture and extends into the core.
4. The puzzle of claim 3 wherein each face centre cubes is of a first plastics material and the axle is a discrete components that passes through an aperture apertures in head region of said cubes and is of a second low-friction plastics material.
The puzzle of claim 4, wherein the low friction material is acetal.
6 The puzzle of claim 4 or 5, wherein the head regions are of ABS.
7. The puzzle of any preceding claim, wherein resilient barb retaining washers snap fit into catch grooves adjacent inner ends of the axles.
8. The puzzle of claim 7, wherein the washers are of acetal.
9. The puzzle of any of claims 1-6, wherein the inner ends of the axles are bifurcated and a retaining washer snap fits into a catch groove adjacent the inner ends of each axle.
10. The puzzle of claim 1, wherein each face centre cubes is formed with a central apcrture, a flanged rctaining collar fits within thc aperture, a fixing scrcw passes through the aperture and extends into the core and an axle with a retaining flange at its inner end has a bore in its outer end into which the fixing screw is threadedly engaged.
11. The puzzle of claim 10, wherein the retaining flange has a non-circular end and fits within an anti-rotation device within the core.
12. The puzzle of any preceding claim, wherein each half-core is generally hemispherical, has three bushings, one of which is in a polar location and two of which are in equatorial locations, and has two equatorially located recesses for receiving bushings of the other half-core.
13. The puzzle of claim 12, wherein the equatorial bushings and the equatorially located recesses are spaced 180° angularly apart, and the equatorial bushings and the equatorial recesses are spaced 90° apart.
14. The puzzle of claim 12 or 13, wherein fastening of the parts of the core is by clips arising from the equatorial bushings of one part that are snap fits within sockets of the other part.
15. The puzzle of any preceding claim, wherein the axles carry coil springs in compression.
16. The puzzle of any of claims 1-14, wherein the axles carry leaf springs in compression.
17. The puzzle of any preceding claim, wherein: the face centre cubes comprise a surface region providing a visible face, four blind faces and a retainer surrounding and projecting outwardly from the four blind faces at their inner ends; and portions of edge and corner cubes are entrapped or hooked under the edge cubes.
18. The puzzle of claim 17, wherein the edge cubes have extensions spaced inwardly from their visible faces for entrapment by adjacent face centre cubes and side faces formed with lateral retainer projections for entrapment beneath portions of adjacent corner cubes
19. The puzzle of claim 18, wherein lateral retainer projections carry inwardly directed spacers.
20. The puzzle of claim 19, wherein opposed ends of the lateral retainer projections of the face centre cubes and/or the inwardly directed spacers carried thereby are bevelled for restoring alignment of a slightly misaligned puzzle as one group of cubes is rotated relative to the others.
21. The puzzle of claim 18, 19 or 20, wherein a set of four face centre cubes and four edge cubes defines a puzzle layer in which portions of the inner retainer flanges of the face centre cubes and lateral retainer projections of the edge cubes project outwardly from each face of the layer and lie along common circles.
22. The puzzle of any of claims 18-21, wherein the corner cubes are each formed at a diagonally inner corner with a concave surface for slideable reception of the retainer of a face centre cube and the lateral retainer projections of an edge cubes, a spacer post arising and extending diagonally inwardly from the concave surface, and a retention plate spaced inwardly of the concave surface for abutment with the extensions of three adjacent edge cubes and positioned so that regions thereof are covered by the face centre cube.
23. The puzzle of claim 22, wherein a face centre cube, a group of four edge cubes and a group of four corner cubes have extensions and support plates defining a part spherical surface complementary to the core.
24. A manipulative puzzle comprising a spherical core, face centre cubes pivotally attached to the core and edge and corner cubes entrapped and retained by the face centre cubes, wherein: the face centre cubes comprise a surface region providing a visible face, four blind faces and a retainer located at the inner ends of the blind faces, said retainer surrounding and projecting outwardly from said faces; the edge cubes each have side faces each formed with a lateral retainer projection for entrapment beneath a portion of an adjacent corner cube and an extension spaced inwardly from its visible faces for entrapment beneath adjacent face centre cubes, said extension being spaced from the remainder of the edge cube to permit the retainer of the a face centre cube to pass as a face of the puzzle is relatively rotated; the corner cubes have a concave surface at a diagonally inner corner for slideable reception of the retainer of a face centre cube and of the lateral retainer projection of an edge cube, a retention plate positioned so that regions thereof are trapped beneath the face centre cube, and a spacer maintaining the retention plate at a spacing inwardly of the concave surface to permit passage of the retainer of a face centre cube and of the lateral retainer projection of an edge cube.
25. The puzzle of claim 24, wherein lateral retainer projections carry inwardly directed spacers.
26. The puzzle of claim 24 or 25, wherein opposed ends of the lateral retainer projections of the face centre cubes and/or the inwardly directed spacers carried thereby are bevelled for restoring alignment of a slightly misaligned puzzle as one group of cubes is rotated relative to the others.
27. The puzzle of claim 24, 2 or 21, w6herein a set of four face centre cubes and four edge cubes defines a puzzle layer in which portions of the inner retainer flanges of the face centre cubes and lateral retainer projections of the edge cubes project outwardly from each face of the layer and lie along common circles.
28. The puzzle of any of claims 24-27, wherein a face centre cube, a group of four edge cubes and a group of four corner cubes have extensions and support plates defining a part spherical surface complementary to the core.
29. A manipulative puzzle comprising a core, face centre cubes pivotally attached to the core and edge and corner cubes entrapped and retained by the face centre cubes, wherein the edge cubes each have side faces each formed with a lateral retainer projection for entrapment beneath a portion of an adjacent corner cube, opposed ends of the lateral retainer projections being bevelled for restoring alignment of a slightly misaligned puzzle as one group of cubes is rotated relative to the others.
30. The puzzle of claim 29, wherein the lateral retainer projections carry inwardly directed spacers and the bevels are formed at opposed ends of the spacers.
31. A manipulative puzzle comprising a core, face centre cubes pivotally attached to the core and edge and corner cubes entrapped and retained by the face centre cubes, wherein internal faces of the edge cubes are bevelled for realignment of a misaligned face of the puzzle on relative rotation of another puzzle face.
32. A corner cube for a 3 x 3 x 3 cubic manipulative puzzle including: a concave surface at a diagonally inner corner for slideable reception of the retainer of a face centre cube and of the lateral retainer projection of an edge cube; a retention plate positioned so that regions thereof are trapped beneath the face centre cube; outwardly directed tabs at edges of the retention plate defining return hooks for entrapment beneath face centre cubes for providing resistance to accidental removal of the corner cube from an assembled puzzle
33. The corner cube of claim 32, further comprising a spacer for maintaining the retention. plate at a spacing inwardly of the concave surface to permit passage of the retainer of a face centre cube and of a lateral retainer projection of an edge cube.
34. A two-part spherical core for a manipulative puzzle, wherein formations on each part provide for core assembly by clipping the parts together and each part has bushings for rotatably supporting axles of face centre cubes.
35. The core of claim 34, wherein clip formations arise from two equatorially located bushings of one core part for reception in in catch sockets of the other core part.
36. The puzzle of claim 35, wherein the equatorial bushings are spaced 1800 angularly apart.
37. A manipulative puzzle comprising a two-part hollow core, face centre cubes pivotally attached to the core and edge and corner cubes held in the puzzle by the face centre cubes, wherein axles are carried by the face centre cubes, springs within the core and carried by the axles urge the face centre cubes inwardly for tensioning the puzzle and each part of the core has bushings that support axles of three of the face centre cubes.
38. The puzzle of claim 37, wherein the axles are of plastics material.
39. The puzzle of claim 38 wherein the face centre cubes are of a fir st plastics material and the axles are discrete components that pass through apertures in head regions of said cubes and are of a second low-friction plastics material.
40. The puzzle of claim 39, wherein the low friction material is acetal.41 The puzzle of claim 39 or 40, wherein the head regions are of ABS.42. A manipulative puzzle comprising a two-part hollow core, face centre cubes pivotally attached to the core and edge and corner cubes held in the puzzle by the face centre cubes, wherein axles are carried by the face centre cubes, springs within the core and carried by the axles urge the face centre cubes inwardly for tensioning the puzzle and clips fasten the parts of the core together.43. A puzzle having a two part spherical core wherein formations on each part provide for core assembly by clipping the parts together and each part has bushings for rotatably supporting axles of face centre cubes and wherein face centre cubes are pivotally attached to the core and edge and corner cubes are entrapped and retained by the face centre cubes, wherein the edge cubes have side faces formed with lateral retainer projections for entrapment beneath portions of adjacent corner cubes.44. The puzzle of claim 43, wherein internal faces of the edge cubes are bevelled for alignment of a misaligned face of the puzzle on relative rotation of another puzzle face.