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TECHNICAL FIELD 
   The present invention relates to building blocks, and more particularly, to releasably attachable building blocks. 
   BACKGROUND OF THE INVENTION 
   A popular type of toy building block is one that has flat surfaces, such as a cube, which can be stacked upon other blocks of like design. Structures made with this type of block are very unstable and can be toppled with the slightest of disturbances. These blocks must also be carefully balanced upon one another, thus limiting the manner in which they can be stacked. 
   Another popular type of toy building block are LINCOLN LOG building blocks which have transverse notches. The logs are stacked by engaging the notched sections of adjacent logs. These types of blocks can be stacked in only a very limited set of alignments. 
   Another popular type of toy building block are LEGO building blocks which have a pattern of projections on the top, and recesses on the bottom for engaging the projections. These types of blocks are stacked upon one another by pressing the projections of one block into the recesses of another. These blocks can be stacked together in a limited number of predetermined locations dictated by the pattern of projections and recesses. 
   There is a need for further building blocks that can be securely and releasably attached together for building relatively stable structures. 
   SUMMARY OF THE INVENTION 
   In a first aspect, the present invention provides a building block that includes a body, an outwardly-extending tapered tongue, and a tapered first groove. The taper of the tongue and the taper of the first groove are substantially the same. The opening of the first groove is wider than a distal portion of the tongue. The distal portion of the tongue is wider than a bottom portion of the first groove. The proximal portion of the tongue is wider than the opening of the tapered first groove. 
   In a second aspect, the present invention provides a building block that includes a body, an outwardly-extending tapered tongue, and a tapered first groove. The taper of the tongue and the taper of the first groove are substantially the same. The block is releasably attachable to another block of the same design by wedging the tongue of the first block into the first groove of the second block. 
   In a third aspect, the present invention provides a base for use in supporting a plurality of building blocks. The base includes a plurality of spaced-apart upwardly extending tongues and a plurality of spaced-apart grooves. The base may be a foundation upon which tongue and groove building blocks can be assembled by inserting the tongues of the building blocks into the grooves of the base and fitting the grooves of the building blocks over the tongues of said base. 
   In a fourth aspect, the present invention provides a tongue and groove joint. The joint comprises a tapered tongue of a first member wedged into a tapered groove of another member. The taper of the tongue and the taper of the groove are substantially the same. The opening of the groove is wider than a distal portion of the tongue. The distal portion of the tongue is wider than the bottom portion of the groove. The proximal portion of the tongue is wider than the opening of the groove. 
   In a fifth aspect, the present invention provides a tongue and groove joint including a first member having a body and a tapered tongue outwardly extending therefrom, and a second member having a body with a tapered groove therein. The tongue of the first member is wedged into the groove of the second member. When the tongue is wedged into the groove, the top of the tongue and the bottom surface of the groove form a gap therebetween, and the body of the first member and the body of the second member form a gap therebetween. 
   In a sixth aspect, the present invention provides a method of forming a tongue and groove joint by providing a first member having a tapered groove, providing a second member having a tapered tongue, and inserting the tapered tongue into the tapered groove. The taper of the tongue and the taper of the groove are substantially the same. The opening of the groove is wider than a distal portion of the tongue. The distal portion of the tongue is wider than a bottom portion of the groove. The proximal portion of the tongue is wider than the opening of the groove. 
   In a seventh aspect, the present invention provides a building block that includes a body and a tapered tongue that extends outwardly from and around the body. 
   In an eighth aspect, the present invention provides a building block that includes a body having a tapered groove that extends around the body. 
   In a ninth aspect, the present invention provides a building block kit including a first building block that has a body with a tapered tongue outwardly extending therefrom, and a second building block that has a body with a tapered groove therein. The first and second building blocks are releasably attachable together upon wedging the tongue of the first building block into the groove of the second building block. 
   Other aspects of the present invention include other building block kits that include the above mentioned blocks and base. 
   These, and other features and advantages of this invention will become apparent from the following detailed description of the various aspects of the invention taken in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, may be best understood by reference to the following detailed description of various embodiments and the accompanying drawings in which: 
       FIG. 1  is an isometric view of a building block in accordance with the present invention; 
       FIG. 2  is an end view of the block of  FIG. 1 ; 
       FIG. 3  is an isometric view of another building block in accordance with the present invention; 
       FIG. 4  is an end view of the block of  FIG. 3 ; 
       FIG. 5  is an isometric view of two blocks of  FIG. 1  joined together; 
       FIG. 6A  is an isometric view of a block of  FIG. 1  joined together with a block of  FIG. 3 ; 
       FIG. 6B  is an exploded isometric view of the blocks of  FIG. 6A ; 
       FIG. 7  is an isometric view of an assembly of six blocks including three blocks of  FIG. 1  and three blocks of  FIG. 3 ; 
       FIG. 8A  is an end view of a tongue and groove joint in accordance with present invention; 
       FIG. 8B  is an exploded end view of the tongue and groove joint of  FIG. 8A ; 
       FIG. 9  is an isometric view of a structure formed from the building blocks and a base in accordance with the present invention; 
       FIG. 10  is an isometric view of the base of  FIG. 9 ; 
       FIG. 11  is an isometric view of another building block having transverse notches in accordance with the present invention; 
       FIG. 12  is an isometric view of another building block having a curved configuration in accordance with the present invention; 
       FIG. 13  is an isometric view of another building block having an angled configuration in accordance with the present invention; 
       FIG. 14  is an isometric view of another building block having a tongue extending outwardly and around the block in accordance with the present invention; and 
       FIG. 15  is an isometric view of another building block having a groove extending around the block in accordance with the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIGS. 1 through 4  show two different embodiments of the building blocks of the present invention. The blocks are tongue and groove blocks that are releasably attachable together by pressing the tongue of one block into a groove of another block as illustrated in  FIGS. 5 ,  6 A,  6 B and  7 . Structures can be made by releasably attaching a plurality of building blocks as shown in  FIG. 9 . The attached blocks can be readily detached from each other simply by pulling the blocks apart from each other. The same blocks can be attached and detached repeatedly. 
   The specific tongue and groove design of the present invention, of which adjacent blocks are releasably attachable, overcomes some of the limitations of currently available building blocks. For example, the present invention provides adjacent blocks that can be assembled in freely variable positions along the tongue and groove longitudinal axes, instead of at a limited number of predetermined positions. This added degree of freedom, combined with the stability of the tongue and groove joint, provides advantages, including, for example, enhanced enjoyment for children playing with toy building blocks of the present invention and the ability of children to make more creative structures than they can with currently available toy building blocks. The stability of structures made using the toy building blocks of the present invention will reduce a child&#39;s frustration that can be caused by some conventional building blocks which can be toppled with the slightest of disturbances. 
   The toy building blocks of the present invention can be suitably sized for handling by children. For example, a toy building block may be about 1–2 inches high and about 1–2 inches wide. A typical child will be capable of easily applying the forces required to assemble and disassemble the toy building blocks of the present invention. 
   The building blocks of the present invention do not require an adhesive or other intermediate bonding material, such as mortar for a typical concrete building block, to form the joint between and attach adjacent blocks. 
   The building blocks of the present invention may be made of wood, plastic, or any other suitable material. 
   With reference again to  FIGS. 1 and 2 , therein illustrated is a building block  10  in accordance with the present invention. The block includes a body  12 , a tapered tongue  14  having two sides  26 , and two inner surfaces  20  forming a tapered groove  18  therebetween. The groove may also be formed by two outwardly-extending legs. The tongue has a distal portion  15   a , a proximal portion  15   b  and may have a top surface  22 . The inner surfaces each have a proximal portion  17   a  and a distal portion  17   b . The groove has a bottom portion  19   a  defined by proximal portion  17   a  of each inner surface  20 , and an opening  19   b  defined by distal portion  17   b  of each inner surface. The body may have surfaces  24  adjacent to the distal portion of each inner surface. Bottom portion  19   a  of groove  18  may have a bottom defined by a bottom surface  28 . Tongue  14  and groove  18  may run a length L of the block. The body of the block may also include shoulders  30  adjacent to the proximal portion of the tongue. 
   With reference to  FIG. 2 , sides  26  of tongue  14  are shown to converge toward each other at an angle A 1 . Inner surfaces  20 , which define groove  18 , are shown to converge toward each other at an angle A 2 . A 1  and A 2  may be substantially the same, so that the tongue and groove are similarly tapered. The angles of convergence (or angle of taper) A 1  and A 2  may be about 14 degrees. Although the tongue is shown to be tapered symmetrically, with both sides  26  inclined at the same angel, for example 7 degrees relative to a common plane, it is understood that the tongue may be tapered asymmetrically with sides  26  each having a different angle of inclination relative to the common plane. Although the groove is shown to be tapered symmetrically with both sides  20  inclined at the same angel, for example 7 degrees relative to a common plane, it is understood that the groove may be tapered asymmetrically with sides  20  each having a different angle of inclination relative to the common plane. The angles of inclination of the sides of the tongue may suitably correspond with the angles of inclination of the sides of the groove for forming a secure and releasably attachable tongue and groove joint. 
   With further reference to  FIG. 2 , tongue  14  has a distal portion with, for example a width W 1 , and a proximal portion with, for example a width W 2 , wherein W 2  is greater than W 1 . The groove has a bottom portion with, for example a width W 3 , and an opening with, for example a width W 4 , wherein W 4  is greater than W 3 . Groove opening width W 4  is wider than a distal portion width W 1  of the tongue. Distal portion width W 1  of the tongue is wider than a bottom portion width W 3  of the groove. Proximal portion width W 2  of the tongue is wider than opening width W 4  of the groove. 
   When a first block  10  and a second block  10  are assembled by inserting the tongue of the first block into the first groove of the second block, as depicted in  FIG. 5 , contact occurs between the sides of the tongue of the first block and the inner surfaces of the second block. The body of the first block and the body of the second block may form gaps  31   a  and  31   b  therebetween. The tongue and a bottom of the groove may form a gap  23  therebetween. When a tongue of one block is pressed into the groove of another block, a tongue and groove joint will form between the two blocks and releasably attach the blocks together. The blocks will be held together by the forces between the sides of the tongue and the inner surfaces forming the sides of the groove. 
   After two blocks which are to be releasably attached have made initial contact between the sides of the tongue and groove, the gaps provide clearance to facilitate further movement of the blocks toward each other when they are further pressed together to form the tongue and groove joint. As the blocks move slightly together, the tongue wedges into the groove, causing compressive forces and resultant friction forces at the tongue and groove interface which hold the adjacent blocks together. 
   The gaps can be made large enough to ensure that, during any anticipated normal use or wedging together of adjacent blocks, there would be no seating contact between the opposite surfaces that form the gaps, for example: between the top of a tongue and the bottom of a first groove; or between the surfaces of the body of the first block and the body of the second block. The gaps can also be made small enough so that the blocks make seating contact between these surfaces upon the application of suitable pressing forces. Such seating contact would limit further relative movement of the blocks toward each other, and thus limit the forces between the sides of the tongue and groove. 
   The gaps can be sized differently to achieve seating at desired surfaces. In addition or in the alternative, separate or integral spacers could be used to achieve localized seating. These options, alone or in combination, can be used to achieve various desired effects, for example limiting stresses between the sides of a tongue and sides of a groove while at the same time providing gaps. Gaps may be desirable for many purposes, such as aesthetic purposes or for receiving mortar. 
   With reference again to  FIGS. 1 and 2 , although sides  26  of the tongue and sides  20  of the groove are shown to be flat, it is understood that they may also be contoured, for example arched, as long as the sides suitably correspond with one another for forming a secure and releasably attachable tongue and groove joint. Groove bottom surface  28  and tongue top surface  22  likewise are shown as flat surfaces but they may also be contoured, such as arched. 
     FIGS. 3 and 4  illustrate a building block  100  in accordance with the present invention. The block has a body  112 , a tapered tongue  114  having two sides  126 , and two inner surfaces  120  forming a tapered first groove  118  therebetween. The tongue has two inner surfaces  142  forming a second groove  140  in the top of tongue  114 . The second groove may have a bottom surface  144 . Second groove  140  may run the length of tongue  114 . The second groove has an opening with, for example a width W 50  ( FIG. 4 ), and a bottom portion with, for example a width W 60  ( FIG. 4 ), wherein W 50  is wider than W 60 . 
   With further reference to  FIG. 4 , tongue  114  has a distal portion with, for example a width W 10 , and a proximal portion with, for example a width W 20 , wherein W 20  is greater than W 10 . Groove  118  has a bottom portion with, for example a width W 30 , and an opening with, for example a width W 40 , wherein W 40  is greater than W 30 . Groove opening width W 40  is wider than a distal portion width W 10  of the tongue. Distal portion width W 10  of the tongue is wider than a bottom portion width W 30  of the groove. Proximal portion width W 20  of the tongue is wider than opening width W 40  of the groove. 
   The second groove, as shown in  FIG. 4 , has its sides  142  converging toward each other at an angle A 30  ( FIG. 4 ). A 30  may be the same as an angle of convergence (or angle of taper) A 10  ( FIG. 4 ) of the side  126  of the tongue and an angle of convergence A 20  ( FIG. 4 ) of the inner surfaces  120 . The second groove, first groove, and tongue may be tapered symmetrically or asymmetrically. A first block  100  and a second block  100  are releasably attachable by inserting tongue  114  of the first block into the first groove  118  of the second block in a similar manner as described above in connection with building block  10 . 
   As shown in  FIGS. 6A and 6B , the first building block  10  of  FIGS. 1 and 2 , can be assembled with the second building block  100  of  FIGS. 3 and 4 , by inserting tongue  14  ( FIG. 6B ) of block  10  into second groove  140  ( FIG. 6B ) of block  100 . The taper of second groove  140  may be substantially the same as the taper of tongue  14 . Width W 50  ( FIG. 6A ) of opening  141   b  ( FIG. 6B ) of second groove  140  is wider than width W 1  ( FIG. 6A ) of distal portion  15   a  ( FIG. 6B ) of tongue  14 . Width W 1  of distal portion  15   a  of tongue  14  is wider than width W 60  ( FIG. 6A ) of bottom portion  141   a  ( FIG. 6B ) of second groove  140 . Width W 2  ( FIG. 6A ) of proximal portion  15   b  ( FIG. 6B ) of tongue  14  is wider than width W 50  of opening  141   b  of second groove  140 . 
   With reference still to  FIGS. 6A and 6B , although sides  142  ( FIG. 6B ) of second groove  140  of block  100  and sides  26  ( FIG. 6B ) of tongue  14  of block  10  are shown to be flat, it is understood that they may also be contoured, for example arched, as long as the sides suitably correspond with one another to form a secure and releasably attachable tongue and groove joint therewith. 
     FIG. 7  shows an assembly of six blocks of the present invention, including three blocks  10  and three blocks  100 . 
     FIGS. 8A and 8B  depict an end view of a tongue and groove joint  400  of the present invention. The joint comprises a tapered tongue  214  ( FIG. 8B ) of a first member  200  wedged into a tapered groove  318  ( FIG. 8B ) of a second member  300 . The taper of the tongue and the taper of the groove may be substantially the same. The opening  319   b  ( FIG. 8B ) of the groove is wider than a distal portion  215   a  ( FIG. 8B ) of the tongue. The distal portion  215   a  of the tongue is wider than the bottom portion  319   a  ( FIG. 8B ) of the groove. The proximal portion  215   b  ( FIG. 8B ) of the tongue is wider than the opening  319   b  of the groove. Member  200  may have shoulders  230  on either side of the tongue. 
   When the tongue of member  200  is inserted into the groove of member  300 , contact occurs between the sides  226  ( FIG. 8B ) of the tongue and the inner surfaces  320  ( FIG. 8B ) forming the groove. The body  212  of member  200  and the body  312  of member  300  may form gaps  431   a  ( FIG. 8A) and 431   b  ( FIG. 8A ) therebetween. The distal end of the tongue and the bottom of the groove may form a gap  423  ( FIG. 8A ) therebetween. When the tongue is pressed into the groove, a tongue and groove joint  400  will form and releasably attach members  200  and  300  together. The blocks will be held together (e.g. horizontally as shown in  FIG. 8A  and along the length of the joint) by the compression and/or friction forces between the sides of the tongue and the inner surfaces forming the groove. 
   With still further reference to  FIGS. 8A and 8B , the size of the gaps may be controlled to achieve certain desired effects as previously discussed above. 
   With still further reference to  FIGS. 8A and 8B , although sides  320  of the groove and sides  226  of the tongue are shown to be flat, it is understood that they may also be contoured, for example arched, as long as they suitably correspond for forming a secure and releasably attachable tongue and groove joint therebetween. 
     FIG. 9  is an isometric view of a structure  500 , such as a toy house, built on a base  550  in accordance with the present invention. The structure comprises a plurality of building blocks of the invention attached together by the tongue and groove means of the present invention. Some of the blocks in the building may comprise flat ends and others may comprise sloped or mitered ends, such as the blocks which form the peaked shape of the top of the building. 
   Base  550  is best illustrated in  FIG. 10 . The base has a plurality of tongues  560  and grooves  570 . The plurality of tongues and grooves are sized to form a releasably attachable tongue and groove joint of the present invention when assembled with the blocks of the present invention. The base may be double-sided, having a different pattern of tongues and grooves on each side. The pattern of tongues and grooves may be designed to provide the foundation for specific sized and shaped buildings, such as historic buildings. The base may also have multiple tiers or levels. 
     FIG. 11  is a broken isometric view of a block  600  having transverse notches  650  in accordance with the present invention. The transverse notches may be across the body  612  or across the tongue  670 . The transverse notch facilitates the engagement of one block with blocks oriented perpendicularly thereto. 
     FIGS. 12 and 13  illustrate blocks  700  and  800  of the present invention having curved and angled configurations along their lengths, respectively. 
   It is understood that the blocks of the present invention can be of any shape in the longitudinal direction. It is also understood that a block may have a plurality of tongues and grooves, for example, each face of the block may have a tongue or a groove. 
     FIG. 14  illustrates block  900  of the present invention having a tongue  910  extending outwardly and around the block. 
     FIG. 15  illustrates block  950  of the present invention having a groove  960  extending around the block. 
   While the invention has been particularly shown and described with reference to certain embodiments, it will be understood by those skilled in the art that various changes in form and details may be made to the invention without departing from the spirit and scope of the invention as described in the following claims.

Summary:
A building block that is releasably attachable to another block of compatible design by wedging the tongue of one block into the groove of another block, without the need for any intermediate adhesives, bonding materials or any other means of holding the blocks together. The block includes a body, an outwardly-extending tapered tongue, and two inner surfaces that form a tapered groove therebetween. The tongue and groove have substantially the same taper. The top of the tongue is wider than the bottom of the groove. The base of the tongue is wider than the opening of the groove. A tongue and groove joint is also disclosed as well as methods for forming a tongue and groove joint. A base which includes a plurality of spaced-apart tongues and grooves is provided for use in supporting a plurality of building blocks thereon.